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• Improved model developed to evaluate a metamaterial-based new cool roof performance. • The model incorporates the spectrum selective approach for radiative sky cooling. • Experiments of the metamaterial-based cool roof are conducted on reduced-size building. • The metamaterial-based cool roof can significantly reduce roof-induced cooling load. A new cool roof with potential to generate significant energy savings in buildings has been developed from a metamaterial film named as RadiCold. Considering that the RadiCold film has unique optical and thermal characteristics and the current Roof Thermal Transfer Value model neglecting the effect of roof thermal mass that may lead to overestimating the cooling load from roofs, this work developed an improved Roof Thermal Transfer Value model and validated the model for both RadiCold cool roof and traditional roofing structures. Data from the reduced-size model building experiments showed that the improved Roof Thermal Transfer Value model can accurately describe the heat gains or losses via the roofs. Under real-world weather conditions in the United States (Tucson AZ, Los Angeles, CA, and Orlando FL), the improved Roof Thermal Transfer Value model has been applied to three types of roof exterior finishing: shingle, Thermoplastic Polyolefin (a cool roof material) and RadiCold. In a typical meteorology year, the modeling results show that the shingle and Thermoplastic Polyolefin roof transfer 78.9–294.1 kWh/(m2·yr) and 8.5–128.2 kWh/(m2·yr) of heat into the building space, respectively, but the RadiCold cool roof dissipates 137.6–268.7 kWh/(m2·yr) of heat from the building space to outdoor environment (e.g., sky). The cooling load reduction from utilizing RadiCold cool roof results in cooling electricity savings of 113.0–143.9 kWh/(m2·yr) compared to the shingle roof and 88.0–92.4 kWh/(m2·yr) compared to the Thermoplastic Polyolefin roof for the three analyzed locations with an assumed air conditioning system's coefficient of performance of 3.0. [ABSTRACT FROM AUTHOR]

• Demonstration of how radiative cooling can reduce water consumption in thermal power plants. • Supplemental radiative cooling system reduces water consumption by 30–90%, without efficiency penalty. • Standalone radiative cooling system eliminates water consumption with 0–2.2% efficiency penalty. • Radiative cooling potential and water saving maps of the contiguous US. Evaporative wet cooling and dry cooling are gradually replacing water-intensive, thermally polluting once-through wet cooling in thermal power plants. Widespread adoption of evaporative wet cooling increases water losses to the atmosphere and still requires uninterrupted makeup water. Dry cooling substantially increases auxiliary power consumption and causes plant efficiency penalty. Therefore, efficient water-saving cooling technologies are of great importance. Here, we explore the water saving potential of day-night radiative sky cooling with and without evaporative wet cooling in thermal power plants. With a radiative cooling system size of 0.0055 km2/MW th normalized by the condenser thermal load at design, we show that a hybrid evaporative-radiative cooling system yields annual water savings of 30–60% in the dry and hot southwestern United States and 50–90% in other parts of the country without causing efficiency penalty. Furthermore, 100% water saving is achievable if the radiative cooling system functions as a stand-alone cooling system, with a much lower efficiency penalty and auxiliary power consumption than that of stand-alone dry cooling systems. [ABSTRACT FROM AUTHOR]